Why does the DataGrid not update when the ItemsSou

问题:

I have a datagrid in my wpf application and I have a simple problem. I have a generic list and I want to bind this collection to my datagrid data source every time an object is being added to the collection. and I'm not interested to use observable collection.

the point is I'm using the same method somewhere else and that works fine. but this time when i press Add button an object is added and datagrid updates correctly but from the second item added to collection datagrid does not update anymore.

Here is the Code :

 private void btnAddItem_Click(object sender, RoutedEventArgs e)
    {
        OrderDetailObjects.Add(new OrderDetailObject
        {
            Price = currentitem.Price.Value,
            Quantity = int.Parse(txtQuantity.Text),
            Title = currentitem.DisplayName,
            TotalPrice = currentitem.Price.Value * int.Parse(txtQuantity.Text)
        });

        dgOrderDetail.ItemsSource = OrderDetailObjects;
        dgOrderDetail.UpdateLayout();
    }

any idea ?

回答1:

The ItemsSource is always the same, a reference to your collection, no change, no update. You could null it out before:

dgOrderDetail.ItemsSource = null;
dgOrderDetail.ItemsSource = OrderDetailObjects;

Alternatively you could also just refresh the Items:

dgOrderDetail.ItemsSource = OrderDetailObjects; //Preferably do this somewhere else, not in the add method.
dgOrderDetail.Items.Refresh();

I do not think you actually want to call UpdateLayout there...

(Refusing to use an ObservableCollection is not quite a good idea)

回答2:

I also found that just doing

dgOrderDetails.Items.Refresh();

would also accomplish the same behavior.

回答3:

If you bind the ItemSource to a filtered list with for example Lambda its not updated. Use ICollectionView to solve this problem (Comment dont work):

//WindowMain.tvTemplateSolutions.ItemsSource = this.Context.Solutions.Local.Where(obj=>obj.IsTemplate); // templates
ICollectionView viewTemplateSolution = CollectionViewSource.GetDefaultView(this.Context.Solutions.Local);
viewTemplateSolution.SortDescriptions.Clear();
viewTemplateSolution.SortDescriptions.Add(new SortDescription("Name", ListSortDirection.Ascending));
viewTemplateSolution.Filter = obj =>
{
   Solution solution = (Solution) obj;
   return solution.IsTemplate;
};
WindowMain.tvTemplateSolutions.ItemsSource = viewTemplateSolution;

回答4:

I got exactly the same problem. I wanted to refresh my datagrid itemssource in code behind, and nothing updated. In fact, it was because I declared the itemssource on datagrid in the xaml file too. That worked on my dev computer but not on the IIS server. If you don't declare itemssource on datagrid in xaml, but just in code behind (when loaded_data and filter or add) it works fine.

Best regards.